One of the industrial revolution's longest constructions celebrates its bicentenary this week.

One of the industrial revolution’s longest constructions celebrates its bicentenary this week.

The mile-long Blisworth Tunnel, on the Grand Union Canal, is the third longest navigable tunnel in the UK.

Staff from British Waterways, the Inland Waterways Association and the Waterways Trust gathered at the mouth of the historic construction near Stoke Bruerne on 21 March as BW chairman George Greener (pictured second from right) unveiled a plaque.

The opening of the tunnel on 25 March 1805 created the final link in the passage between London and the industrial Midlands and northern England.

It took 12 years to build, using no mechanical aids beyond pick, shovel, wheelbarrow and gunpowder. During construction the tunnel collapsed killing 14 people.

In 1980, BW began a £4.5m project to rebuild the central section of the tunnel and it re-opened in 1984.

Blisworth can fit two 7ft-wide narrowboats. Craft wider than 7ft must give advance notice so boats can be prevented from entering the tunnel at the opposite end.

The longest navigable tunnel in Britain is Standedge at 3 miles, while the second longest is Dudley at just under two miles.